Temperature changes off the coast dried out East Africa 2 million years ago

By Alexandra Witze, 17:09 PM February 18, 2012

VANCOUVER — Scientists may now be able to explain one of the key events that shaped human history: why East Africa got drier starting around 2 million years ago, with forests giving way to grasslands on which Homo could further evolve. Ocean temperature changes, especially the arrival of a strong warm/cool difference along the equator in the Indian Ocean, could have triggered the change.

“Those gradients are responsible for shifting rainfall towards or away from East Africa,” said Peter deM...